CN103618335B - A kind of control method for photovoltaic combining inverter low voltage crossing - Google Patents
A kind of control method for photovoltaic combining inverter low voltage crossing Download PDFInfo
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Abstract
The invention provides a kind of control method for photovoltaic combining inverter low voltage crossing, the method comprises the following steps: obtain three-phase voltage signal and the three-phase current signal of inverter output end of three phase network；Determine the DC current component under the dq axle DC component of three-phase power grid voltage and synchronous rotary dq axis coordinate system；Obtain photovoltaic array output voltage and photovoltaic array output electric current；Judge whether three-phase power grid voltage is fallen；The d axle reference current of inverter is obtained when three-phase power grid voltage is normal；The d axle reference current of inverter is obtained when three-phase power grid voltage is fallen；Pi regulator is used to obtain width-modulation pulse according to the d axle reference current of described inverter；PID regulator is used to obtain width-modulation pulse according to the d axle reference current of described inverter.The method applies to dynamic response quick and smooth and the photovoltaic combining inverter low voltage traversing control method of good stability that three phase network symmetry is fallen.
Description
Technical field
The present invention relates to a kind of method that photovoltaic generating system controls technical field, in particular to one is for photovoltaic grid-connected inversion
The control method of device low voltage crossing.
Background technology
Low voltage ride-through capability is one of important grid-connected index of wind-powered electricity generation, photovoltaic distributed electricity generation system, steady to the safety of electrical network
Surely run significant.Although relevant criterion, control technology and the test device etc. of wind energy turbine set are carried out by Chinese scholars
Research, achieves certain scientific research and industry achievement；The wind-power electricity generation big country such as Denmark, Germany has formulated new electrical network fortune in succession
Row criterion, it is desirable to wind power system has low voltage ride-through capability, but for photovoltaic system, China the most not yet puts into effect light
Lie prostrate grid-connected national standard, the company standard " photovoltaic plant accesses electric power network technique regulation " that only State Grid Corporation of China formulates at it
(Q/GDW618-2011) in, the low voltage crossing to big-and-middle-sized photovoltaic plant has carried out certain specification, the most domestic by low electricity
Pressure passes through test, and especially no-voltage passes through the photovoltaic combining inverter of test is also relatively small part, and domestic photovoltaic industry is sent out
Rapidly, by the end of the year 2010, the installed capacity of China's grid-connected photovoltaic power generation has reached 900,000 kilowatts in exhibition, it is contemplated that the year two thousand twenty installation total amount
Being up to 20,000,000-5,000 ten thousand kilowatts, this controls skill to the research of grid-connected key technology, especially photovoltaic low voltage crossing
The research and development of art bring enormous pressure.
Photovoltaic combining inverter is carrying out low voltage crossing test at present, when especially no-voltage passes through test, is primarily present two
The problem of aspect: 1, grid voltage sags and recovery moment, due to the dynamic controlling of photovoltaic combining inverter DC bus-bar voltage
Can be deteriorated causes DC bus-bar voltage to vibrate, and even further results in control system unstability, and inverter is had to and grid disconnection；2、
Grid voltage sags and recovery moment, especially when the catastrophe failure that three-phase power grid voltage occurs symmetry to drop to no-voltage, inverse
Become the three-phase electricity outflow that device causes inverter export owing to the energy having little time to will build up in inverter smoothly flows to electrical network
The biggest spike or vibration, once exceed inverter current protection threshold value and and grid disconnection, it is impossible to realize low voltage crossing therefore
Not off-grid during barrier runs this basic technical indicator, i.e. low voltage crossing test crash.
It is applicable to the photovoltaic of dynamic response quick and smooth that three phase network symmetry falls and good stability also accordingly, it is desirable to provide a kind of
Net inverter low voltage traversing control method.
Summary of the invention
For overcoming above-mentioned the deficiencies in the prior art, the present invention provides a kind of controlling party for photovoltaic combining inverter low voltage crossing
Method, the photovoltaic combining inverter that the method applies to dynamic response quick and smooth that three phase network symmetry falls and good stability is low
Voltage ride-through control method.
Realizing the solution that above-mentioned purpose used is:
A kind of control method for photovoltaic combining inverter low voltage crossing, it thes improvement is that: described method includes following
Step:
I, the three-phase voltage signal obtaining three phase network and the three-phase current signal of inverter output end；
DC current component under II, the dq axle DC component determining three-phase power grid voltage and synchronous rotary dq axis coordinate system；
III, acquisition photovoltaic array output voltage and photovoltaic array output electric current；
IV, judge whether three-phase power grid voltage is fallen；
V, when three-phase power grid voltage is normal obtain inverter d axle reference current；
VI, when three-phase power grid voltage is fallen obtain inverter d axle reference current；
VII, utilization pi regulator obtain width-modulation pulse according to the d axle reference current of described inverter；
VIII, utilization PID regulator obtain width-modulation pulse according to the d axle reference current of described inverter.
Further, in described step II, determine three-phase electricity respectively according to described three-phase voltage signal and described three-phase current signal
DC current component under the dq axle DC component of net voltage and synchronous rotary dq axis coordinate system, including:
Phase-locked loop pll method is used to determine line voltage Vector Rotation angle, θ, according to described electricity according to described three-phase voltage signal
The net voltage vector anglec of rotation and described three-phase voltage signal determine d, q axle DC component e of three-phase power grid voltaged、eq；
Three-phase current signal and described line voltage Vector Rotation angle according to described inverter output end carry out dq rotating vector change
Change, determine the DC current component i under synchronous rotary dq axis coordinate systemd、iq。
Further, described step IV includes: judge whether three-phase power grid voltage is fallen, if described three-phase power grid voltage is normal,
Enter step V, if described three-phase power grid voltage is fallen, enter step VI.
Further, described step V comprises the following steps:
If the described three-phase power grid voltage of S501 is normal, export electric current according to described photovoltaic array output voltage and described photovoltaic array,
Maximal power tracing MPPT method is used to determine maximum power point of photovoltaic array reference voltage；
S502, the difference of described photovoltaic array output voltage and described maximum power point of photovoltaic array reference voltage is carried out voltage ratio
Electric current i is obtained after example integral PI actuatord1；
S503, by described electric current id1It is assigned to the d axle reference current i of inverter outputdref；For making inverter output current and electrical network
Voltage in phase, arranges the q axle reference current i of inverter outputqref=0, enter step VII.
Further, described step VI includes:
If described three-phase power grid voltage generation symmetry is fallen, then latch the photovoltaic array output voltage u falling the momentpvAnd upper one sampling
The electric current i in momentd1, and the i always this latched during fallingd1Electric current latched value i after being multiplied with coefficient kd2It is assigned to inversion
The d axle reference current i of device outputdref, k span is 0.5 to 1；The q axle reference current i of inverter output is setqref=0,
Enter step VIII；
If three-phase power grid voltage recovers normal again from falling state, recover the moment by described voltage latch value upvIt is assigned to photovoltaic battle array
Row maximum power point reference voltage, returns step S502.
Further, described step VII comprises the following steps:
The d axle reference current of S701, described inverter output and described electric current idDifference adjust through the first current ratio integral PI
After joint device, with q axle cross-couplings item-wLiqD axle DC component e with described three-phase power grid voltagedAddition obtains ud；
S702, the q axle reference current that inverter is exported and described electric current iqDifference regulate through the second current ratio integral PI
After device, with d axle cross-couplings item wLidQ axle DC component e with described three-phase power grid voltageqAddition obtains uq, wherein, w
For the angular frequency of three-phase power grid voltage, L is the filter inductance of grid-connected wave filter in inverter；
S703, described line voltage Vector Rotation angle, θ are by udAnd uqCarry out Parker Park inverse transformation, it is thus achieved that two-phase static coordinate
U under XiαAnd uβ；Use space vector pulse width modulation SVPWM method, obtain 6 tunnel pulsewidths through digital signal processor processes
Modulation pulse, returns step IV and continues monitoring.
Further, described step VIII comprises the following steps:
The d axle reference current of S801, described inverter output and described electric current idDifference through the first current ratio integral PID
After actuator, with q axle cross-couplings item-wLiqD axle DC component e with described three-phase power grid voltagedAddition obtains ud1；
S802, the q axle reference current that inverter is exported and described electric current iqDifference through the second current ratio integral differential PID
After actuator, with d axle cross-couplings item wLidQ axle DC component e with described three-phase power grid voltageqAddition obtains uq1, wherein,
W is the angular frequency of three-phase power grid voltage, and L is the filter inductance of grid-connected wave filter in inverter；
S803, described line voltage Vector Rotation angle, θ are by ud1And uq1Carry out Parker Park inverse transformation, it is thus achieved that the static seat of two-phase
U under mark systemα1And uβ1；Use space vector pulse width modulation SVPWM method, obtain 6 tunnels through digital signal processor processes
Width-modulation pulse, returns step IV and continues monitoring.
Compared with prior art, the method have the advantages that
(1) the method dynamic response quick and smooth of the present invention, owing to when three-phase power grid voltage generation symmetry is fallen, latching this and falling
Fall the photovoltaic array output voltage u in momentpv, and when detect three-phase power grid voltage from fall state again recover normal time, then will
This u latchedpvIt is assigned to maximum power point of photovoltaic array reference voltage uref, make DC bus-bar voltage in three-phase power grid voltage from falling
Dynamic transition process vibration when the state that falls is recovered normal again is less, and quickly decays and converge to stationary value, the most greatly carries
The high dynamic response capability of DC bus-bar voltage outer shroud, makes DC bus-bar voltage the most extensive from falling state in three-phase power grid voltage
Dynamic transition process time the most normal is more smooth, reduces the impact to dc-link capacitance, improves the use of dc-link capacitance
Life-span.
(2) stablizing of the inventive method good stability, and flexible adjustment, energy efficiency during can fully taking into account fault and system
Property, i.e. during fault from the standpoint of energy efficiency maximum, can pay the utmost attention to arrange k=1, it is achieved it is right to occur in three-phase power grid voltage
When claiming the catastrophe failure dropping to no-voltage, monopole three-phase photovoltaic grid-connected inverter remains to stably to three phase network conveying and electricity
An equal amount of three-phase current when net does not breaks down, it is ensured that still carry power as much as possible to electrical network during fault traversing；
Certainly also dependent on the system stability situation of on-the-spot actual debugging, in the span of 0.5 to 1, the setting value of k is changed flexibly,
The size of the three-phase current of electrical network can be input to by photovoltaic combining inverter during suitably reducing fault, fully ensure electrical network electricity
Pressure symmetry is fallen period photovoltaic combining inverter and can be stably incorporated into the power networks.
(3) the inventive method failure response speed is fast, due to when monitoring three-phase power grid voltage and falling, and the inventive method
Quickly increase D actuator on the basis of the pi regulator under the operating mode that is normally incorporated into the power networks, i.e. use PID regulator according to described
The d axle reference current of inverter obtains width-modulation pulse, drastically increases system in event by the introducing of this D actuator
Barrier occurs and recovers the fast-response energy in moment, effectively inhibits the current spike of instant of failure.
Accompanying drawing explanation
Fig. 1 is typical monopole three-phase photovoltaic grid-connected inverter system block diagram；
Fig. 2 is key waveforms figure in photovoltaic combining inverter no-voltage crossing process.
Detailed description of the invention
Below in conjunction with the accompanying drawings the detailed description of the invention of the present invention is described in further detail.
As it is shown in figure 1, Fig. 1 is typical monopole three-phase photovoltaic grid-connected inverter system block diagram；In figure, photovoltaic DC-to-AC converter low-voltage
The controller passed through is connected with photovoltaic DC-to-AC converter to be controlled, obtains the signal value of described photovoltaic DC-to-AC converter successively, uses above-mentioned side
Method carries out the control of low voltage crossing to it.The controller of low voltage ride through of photovoltaic inverter includes the place for analytical calculation signal
Manage device and for analyzing the digital signal processor DSP obtaining 6 road width-modulation pulses.The control of low voltage ride through of photovoltaic inverter
Device processed realizes the control method for photovoltaic combining inverter low voltage crossing that the present invention proposes, and the method comprises the following steps:
Step one, the three-phase voltage signal obtaining three phase network and the three-phase current signal of inverter output end；
Step 2, determine respectively according to three-phase voltage signal and three-phase current signal three-phase power grid voltage dq axle DC component and with
Step rotates the DC current component under dq axis coordinate system；
Step 3, acquisition photovoltaic array output voltage upvElectric current i is exported with photovoltaic arraypv；
Step 4, judge whether three-phase power grid voltage is fallen；
Step 5, when three-phase power grid voltage is normal obtain inverter d axle reference current；
Step 6, when three-phase power grid voltage is fallen obtain inverter d axle reference current；
Step 7, utilization pi regulator obtain width-modulation pulse according to the d axle reference current of inverter；
Step 8, utilization PID regulator obtain width-modulation pulse according to the d axle reference current of inverter.
In step 2, phase-locked loop pll method is used to determine line voltage Vector Rotation angle, θ according to three-phase voltage signal, according to
Line voltage Vector Rotation angle and three-phase voltage signal determine d, q axle DC component e of three-phase power grid voltaged、eq；
Three-phase current signal and line voltage Vector Rotation angle according to inverter output end carry out dq rotating vector conversion, determine
DC current component i under synchronous rotary dq axis coordinate systemd、iq。
In step 3, detection obtains photovoltaic array output voltage upvElectric current i is exported with photovoltaic arraypv；
In step 4, it is judged that whether three-phase power grid voltage is fallen, if three-phase power grid voltage normally, enters step 5, if three-phase electricity
Net Voltage Drop then enters step 6.
In step 5, if three-phase power grid voltage is normal, exports electric current according to photovoltaic array output voltage and photovoltaic array, use
High-power tracking MPPT method disturbance observational method determines maximum power point of photovoltaic array reference voltage uref；
By photovoltaic array output voltage and maximum power point of photovoltaic array reference voltage urefDifference carry out voltage ratio integral PI tune
Electric current i is obtained after joint deviced1, wherein, electric current id1For obtaining the intermediate variable of d axle reference current；
By electric current id1It is assigned to the d axle reference current i of inverter outputdref, and for making inverter output current same with line voltage
Phase place, arranges the q axle reference current i of inverter outputqref=0, enter step 7.
In step 6, if three-phase power grid voltage generation symmetry is fallen, then latch this upper sampling instant falling the moment, such as step
Electric current i obtained by fived1, obtain this electric current latched value id1Value after being multiplied with coefficient k is designated as id2, 0.5≤k≤1, and latch
This fall the moment by the photovoltaic array output voltage u obtained by step 3pv, remember that this voltage latch value is upv2；Above-mentioned electric current id1
With electric current id2It is the intermediate variable obtaining d axle reference current；
If three-phase power grid voltage is not normal, the most always by electric current latched value i from falling recovering stated2It is assigned to the d of inverter output
Axle reference current idref, the q axle reference current i of inverter output is setqref=0, enter step 7；
If three-phase power grid voltage recovers normal again from falling state, then again recover the moment in three-phase power grid voltage, voltage is locked
Deposit value upv2It is assigned to maximum power point of photovoltaic array reference voltage uref, by photovoltaic array output voltage upvMaximum with photovoltaic array
Power points reference voltage urefDifference carry out obtaining after voltage ratio integral PI actuator electric current id1；
By electric current id1It is assigned to the d axle reference current i of inverter outputdref, and for making inverter output current same with line voltage
Phase place, arranges the q axle reference current i of inverter outputqref=0, enter step 7.That is, the method as described in step 5 obtains
The d axle reference current of inverter.
In step 7, the d axle reference current of inverter output and electric current idDifference through the first current ratio integral PI actuator
After, with q axle cross-couplings item-wLiqD axle DC component e with described three-phase power grid voltagedAddition obtains ud；
The q axle reference current that inverter is exported and described electric current iqDifference after the second current ratio integral PI actuator,
With d axle cross-couplings item wLidQ axle DC component e with described three-phase power grid voltageqAddition obtains uq, wherein, w is three-phase
The angular frequency of line voltage, L is the filter inductance of grid-connected wave filter in inverter；
Line voltage Vector Rotation angle, θ is by udAnd uqCarry out Parker Park inverse transformation, it is thus achieved that the u under two-phase rest frameαWith
uβ；Use space vector pulse width modulation SVPWM method, process through digital signal processor DSP and obtain 6 tunnel pulsewidth modulations
Pulse, PWM1～PWM6, enter step 5.
In step 8, the d axle reference current of inverter output and described electric current idDifference through the first current ratio integral PID
After actuator, with q axle cross-couplings item-wLiqD axle DC component e with described three-phase power grid voltagedAddition obtains d axle electricity
Pressure ud1；
The q axle reference current that inverter is exported and described electric current iqDifference regulate through the second current ratio integral differential PID
After device, with d axle cross-couplings item wLidQ axle DC component e with described three-phase power grid voltageqAddition obtains q shaft voltage uq1,
Wherein, w is the angular frequency of three-phase power grid voltage, and L is the filter inductance of grid-connected wave filter in inverter；
Described d shaft voltage ud1With described q shaft voltage uq1For medium voltage variable, line voltage Vector Rotation angle, θ is by ud1With
uq1Carry out Parker Park inverse transformation, it is thus achieved that the u under two-phase rest frameα1And uβ1；Use space vector pulse width modulation SVPWM
Method, processes through digital signal processor DSP and obtains 6 road width-modulation pulse PWM1～PWM6, return step 5.
Embodiment
As in figure 2 it is shown, Fig. 2 is key waveforms figure in photovoltaic combining inverter no-voltage crossing process；In conjunction with real-timedigital simulation
Instrument RTDS (Real-Time Digital Simulator) uses the low-voltage of the monopole three-phase photovoltaic grid-connected inverter of the present invention to wear
More control method inverter monopole three-phase photovoltaic grid-connected to 250kW carries out the emulation under three-phase power grid voltage symmetry is fallen, and provides three
Phase line voltage symmetry drops to the simulation example of no-voltage, and the present invention is described in further detail.
System control block figure when the system topology of the present embodiment and electrical network are normal is as it is shown in figure 1, the 250kW photovoltaic battle array that uses
Row normal environment conditions (intensity of illumination R=1kW/m2, ambient temperature T=25 DEG C) under parameter be: maximum power point voltage
Umax=455V, maximum power point electric current Imax=545.6A, open-circuit voltage Uoc=650V, short circuit current Isc=600A；
Circuit system parameter is: DC bus capacitance electric capacity C=10000uF, the filter inductance L=0.4mH of grid-connected wave filter, and
The filter resistance R=0.02 Ω of net wave filter, simulation step length Ts=50 μ S；Controller parameter is: coefficient k=1, voltage ratio
The proportionality coefficient of integral PI actuator and integral coefficient are respectively 0.06 and 0.25；First current ratio integral PI actuator
Proportionality coefficient and integral coefficient are respectively 1.2 and 1；Proportionality coefficient and the integral coefficient of the second current ratio integral PI actuator divide
It is not 1.2 and 1；Proportionality coefficient, integral coefficient and the differential coefficient of the first current ratio integral differential PID regulator is respectively
1.35,10 and 0.5；The proportionality coefficient of the second current ratio integral differential PID regulator, integral coefficient and differential coefficient are respectively
It is 1.35,10 and 0.5；The angular frequency w of three-phase power grid voltage is 314rad/s.
Use the simulated effect of the inventive method as in figure 2 it is shown, as seen from the figure:
1) by inverter output end A, B, C three-phase current signal i in Fig. 2a、ibAnd icVisible, due in three-phase power grid voltage
During whole symmetry drops to no-voltage, have been used up PID PID regulator, by introducing this differentiation element, very
Three-phase power grid voltage symmetry is quickly inhibited well to fall " spike " of the three-phase grid electric current that moment is caused；It addition, by Fig. 2
Middle photovoltaic array output voltage upvVisible, owing to when three-phase power grid voltage generation symmetry is fallen, latching this photovoltaic falling the moment
Array output voltage upv, and when detect three-phase power grid voltage from fall state again recover normal time, then the u that this is latchedpvCompose
Value is to maximum power point of photovoltaic array reference voltage uref, improve the dynamic response capability of DC bus-bar voltage outer shroud, make direct current female
Line voltage is less from the dynamic transition process vibration fallen when state is recovered normal again in three-phase power grid voltage, and quickly decays also
Converge to stationary value；
2) by inverter output end A, B, C three-phase current signal i in Fig. 2a、ibAnd icVisible, owing to detecting three phase network
When voltage generation symmetry is fallen, latch the electric current i of this upper sampling instant falling the momentd1, and this is locked falling period always
The i depositedd1The d axle reference current i of inverter output it is assigned to span coefficient k between 0.5 to 1 after being multiplieddref,
Therefore whole fall period, actually given up three-phase power grid voltage normal time DC bus-bar voltage outer shroud control part, directly
Connect employing synchronizing current vector PID controller, and the present embodiment successfully passes coefficient k=1 is set successfully maintains three phase network
Three phase network electric current during Voltage Drop and three-phase power grid voltage three phase network electric current time normal is basically identical, it is ensured that three
When phase line voltage occurs symmetry to drop to the catastrophe failure of no-voltage, monopole three-phase photovoltaic grid-connected inverter remain to stably to
An equal amount of three-phase current when three phase network conveying is not broken down with electrical network；It addition, can according to on-the-spot actual debugging situation,
The setting value of k is changed flexibly in the span of 0.5 to 1, i.e. defeated by photovoltaic combining inverter during suitably reducing fault
Enter the size of the three-phase current to electrical network, fully ensure that line voltage symmetry is fallen period photovoltaic combining inverter and can be stablized grid-connected fortune
OK, summary is described, and the inventive method can fully be guaranteed in line voltage symmetry and fall photovoltaic combining inverter under operating mode and can stablize reality
Existing low voltage crossing runs.
The method of the present invention is a kind of to be applicable to the photovoltaic of dynamic response quick and smooth that three phase network symmetry falls and good stability also
Net inverter low voltage traversing control method, the method using the present invention, if detecting, three-phase power grid voltage is normal, then by often
Maximum power point tracing method and DC bus-bar voltage actuator obtain electric current id1, and it is assigned to the d of inverter output
Axle reference current idref, the q axle reference current i of inverter output is setqref=0, use synchronizing current vector PI controller and sky
Between Vector Pulse Width Modulation method obtain 6 road width-modulation pulses；If detecting, three-phase power grid voltage generation symmetry is fallen, then latch
This falls the photovoltaic array output voltage u in momentpv, latch the electric current i of this upper sampling instant falling the moment simultaneouslyd1, and falling
The i always this latched during fallingd1The d axle of inverter output it is assigned to value coefficient k in the range of 0.5 to 1 after being multiplied
Reference current idref, to be checked measure the u that this latched again when three-phase power grid voltage is recovered normalpvIt is assigned to photovoltaic array peak power
Point reference voltage uref, the q axle reference current i of inverter output is setqref=0, use synchronizing current vector PID controller and
Space vector width pulse modulation method obtains 6 road pulse-width modulation PWM pulses.
Finally should be noted that: above example is merely to illustrate the technical scheme of the application rather than the restriction to its protection domain,
Although being described in detail the application with reference to above-described embodiment, those of ordinary skill in the field are it is understood that this area
Technical staff still can carry out all changes, amendment or equivalent to the detailed description of the invention of application after reading the application, but
These changes, amendment or equivalent, all within the claims that application is awaited the reply.
Claims (2)
1. the control method for photovoltaic combining inverter low voltage crossing, it is characterised in that: described method includes following step
Rapid:
I, the three-phase voltage signal obtaining three phase network and the three-phase current signal of inverter output end；
DC current component under II, the dq axle DC component determining three-phase power grid voltage and synchronous rotary dq axis coordinate system；
III, acquisition photovoltaic array output voltage and photovoltaic array output electric current；
IV, judge whether three-phase power grid voltage is fallen；
V, when three-phase power grid voltage is normal obtain inverter d axle reference current；
VI, when three-phase power grid voltage is fallen obtain inverter d axle reference current；
VII, utilization pi regulator obtain width-modulation pulse according to the d axle reference current of described inverter；
VIII, utilization PID regulator obtain width-modulation pulse according to the d axle reference current of described inverter；
In described step II, determine the dq of three-phase power grid voltage respectively according to described three-phase voltage signal and described three-phase current signal
DC current component under axle DC component and synchronous rotary dq axis coordinate system, including:
Phase-locked loop pll method is used to determine line voltage Vector Rotation angle, θ, according to described electricity according to described three-phase voltage signal
The net voltage vector anglec of rotation and described three-phase voltage signal determine d, q axle DC component e of three-phase power grid voltaged、eq；
Three-phase current signal and described line voltage Vector Rotation angle according to described inverter output end carry out dq rotating vector change
Change, determine the DC current component i under synchronous rotary dq axis coordinate systemd、iq；
Described step IV includes: judge whether three-phase power grid voltage is fallen, if described three-phase power grid voltage is normally, enters step V,
If described three-phase power grid voltage is fallen, enter step VI；
Described step V comprises the following steps:
If the described three-phase power grid voltage of S501 is normal, export electric current according to described photovoltaic array output voltage and described photovoltaic array,
Maximal power tracing MPPT method is used to determine maximum power point of photovoltaic array reference voltage；
S502, the difference of described photovoltaic array output voltage and described maximum power point of photovoltaic array reference voltage is carried out voltage ratio
Electric current i is obtained after example integral PI actuatord1；
S503, by described electric current id1It is assigned to the d axle reference current i of inverter outputdref；For making inverter output current and electrical network
Voltage in phase, arranges the q axle reference current i of inverter outputqref=0, enter step VII；
Described step VI includes:
If described three-phase power grid voltage generation symmetry is fallen, then latch the photovoltaic array output voltage u falling the momentpvAnd upper one sampling
The electric current i in momentd1, and the i always this latched during fallingd1Electric current latched value i after being multiplied with coefficient kd2It is assigned to inversion
The d axle reference current i of device outputdref, k span is 0.5 to 1；The q axle reference current i of inverter output is setqref=0,
Enter step VIII；
If three-phase power grid voltage recovers normal again from falling state, recover the moment by described voltage latch value upvIt is assigned to photovoltaic battle array
Row maximum power point reference voltage, returns step S502；
Described step VII comprises the following steps:
The d axle reference current of S701, described inverter output and described electric current idDifference adjust through the first current ratio integral PI
After joint device, with q axle cross-couplings item-wLiqD axle DC component e with described three-phase power grid voltagedAddition obtains ud；
S702, the q axle reference current that inverter is exported and described electric current iqDifference regulate through the second current ratio integral PI
After device, with d axle cross-couplings item wLidQ axle DC component e with described three-phase power grid voltageqAddition obtains uq, wherein, w
For the angular frequency of three-phase power grid voltage, L is the filter inductance of grid-connected wave filter in inverter；
S703, described line voltage Vector Rotation angle, θ are by udAnd uqCarry out Parker Park inverse transformation, it is thus achieved that two-phase static coordinate
U under XiαAnd uβ；Use space vector pulse width modulation SVPWM method, obtain 6 tunnel pulsewidths through digital signal processor processes
Modulation pulse, returns step IV and continues monitoring.
A kind of control method for photovoltaic combining inverter low voltage crossing, it is characterised in that:
Described step VIII comprises the following steps:
The d axle reference current of S801, described inverter output and described electric current idDifference through the first current ratio integral PID
After actuator, with q axle cross-couplings item-wLiqD axle DC component e with described three-phase power grid voltagedAddition obtains ud1；
S802, the q axle reference current that inverter is exported and described electric current iqDifference through the second current ratio integral differential PID
After actuator, with d axle cross-couplings item wLidQ axle DC component e with described three-phase power grid voltageqAddition obtains uq1, wherein,
W is the angular frequency of three-phase power grid voltage, and L is the filter inductance of grid-connected wave filter in inverter；
S803, described line voltage Vector Rotation angle, θ are by ud1And uq1Carry out Parker Park inverse transformation, it is thus achieved that the static seat of two-phase
U under mark systemα1And uβ1；Use space vector pulse width modulation SVPWM method, obtain 6 tunnels through digital signal processor processes
Width-modulation pulse, returns step IV and continues monitoring.
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